Additive for inhibiting caking and freezing of sodium chloride and for inhibiting corrosion in the presence of sodium chloride brine

ABSTRACT

A SURFACE ACTIVE AGENT, CALCIUM, CHLORIDE, FERROCYANIDE ION AND BORAX ADMIXED TO PROVIDE AN ADDITIVE FOR INHIBITING CAKING, FREEZING AND INHIBITING CORROSION WITH RESPECT TO PARTICULATE SODIUM CHLORIDE.

United States Patent 0 ADDITIVE FOR INHIBITING CAKING AND FREEZ- ING OF SODIUM CHLORIDE AND FOR INHIBIT- ING CORROSION IN THE PRESENCE OF SODIUM CHLORIDE BRINE Charles H. Jacoby, Grosse Ile, and Frank V. Whelply,

Dearborn, Mich., assignors to International Salt Company, Clark Summit, Pa. No Drawing. Filed May 10, 1966, Ser. No. 548,837

The portion of the term of the patent subsequent to Apr. 16, 1985, has been disclaimed Int. Cl. C09k 3/18 US. Cl. 252383 2 Claims ABSTRACT OF THE DISCLOSURE A surface active agent, calcium chloride, ferrocyanide ion and borax admixed to provide an additive for inhibiting caking, freezing and inhibiting corrosion with respect to partculate sodium chloride.

This invention relates to additives for particulate sodium chloride and is directed in particular to an additive having the simultaneous characteristics of inhibiting caking and freezing of sodium chloride and of inhibiting corrosion which may occur incidental to the presence of a sodium chloride brine.

The use of bulk particulate sodium chloride for the control and removal of ice and snow on vehicular thoroughfares has gained wide acceptance within recent years. Consequently, the storage and shipment of large quantities of bulk salt is involved in highway ice and snow control. Historically, the earliest problem encountered with respect to the shipment and storage of such salt was that of caking and it was also the first solved. The solution to this problem lies in the discovery that the addition of minor amounts of one or more water soluble complex iron cyanides will inhibit caking, see Pat. No. 3,036,884, issued May 29, 1962. Next it was discovered that freezing of the salt mass, even when treated as above, particularly during transit during winter months, can be a serious problem in this field. Since it is well known that caking and freezing of bulk particulate sodium chloride are separate and distinct phenomena, it is not surprising that the aforesaid water soluble complex iron cyanide anti-caking additives had little effect on the freezing tendency of bulk particulate sodium chloride.

However, it has been discovered recently that certain formulations comprising a synthetic surface active agent and either or both calcium chloride together with a water soluble complex iron cyanide are effective to inhibit both caking and freezing of bulk particulate sodium chloride. For complete details on such formulations, reference is had to our copending previous applications: 345,859, filed Feb. i9, 1964 and now abandoned; 443,668, filed Mar. 29, l965; 466,060, filed June 22, 1965; 466,409, filed June 23, 1965, now Pat. No. 3,383,317; and 467,739, filed June 28, 1965, now Pat. No. 3,396,112.

In addition to the aforesaid problems of caking and freezing, the additional problem of corrosion which may occur incidental to the presence of sodium chloride brines presents itself. The mechanism of corrosion associated With the use of rock salt for snow and ice removal, and particularly as it affects automobiles and structural metal elements along a highway (i.e., bridges, manhole covers, metal gratings and the like), is unquestionably of complex character particularly when one considers the fact that the strength of the brine solutions which may be involved will vary over a wide range, from very dilute to fully saturated. Although the mechanism is complex, it is known that corrosion in the presence of sodium (ill ice

chloride brines proceeds more rapidly in dilute sodium chloride brines, being at a maximum at about 2.5% brine. and that the effect diminishes rapidly from this maximum so that after about 1520% brine strength the eflect is relatively insignificant.

In connection with the last mentioned additives, it was observed that they displayed tendencies, in varying degrees, to inhibit corrosion of ferrous metals exposed to brines consisting of aqueous solutions of sodium chloride treated with the additives. If, however, one compares the anti-corrosive effects of these additives with the effect produced by well known anti-corrosion agents for sodium chloride brines, as for example sodium chromate or sodium hexametaphosphate, such additives do not compare with sufficient favor as to deserve commercial attention in this respect. At the same time, there is a need for an additive of the nature described having, in addition to its anti-caking and anti-freezing characteristics, the ability to combat corrosion to a degree which at least compares favorably with the effect of conventional anticorrosion agents as aforesaid, since these conventional anti-corrosion agents, though effective, introduce certain ancillary problems. Specifically, the conventional agents are costly, they are toxic and they are apt to pollute ground water supplies. The formulations according to this invention are anti-caking, anti-freezing agents which are also effective to inhibit corrosion to a degree lying between the respective effects of sodium hexametaphosphate and sodium chromate, it being well known that the conventional agent, sodium hexametaphosphate, is less effective than the conventional agent, sodium chromate.

This invention is specifically directed to the discovery that a particular one of the formulations according to the aforementioned copending applications, when combined with a borax compound attains such a high degree of anti-corrosion effect as to surpass the anti-corrosion effect of sodium hexametaphosphate conventionally used with sodium chloride brines and does so Without degrading the anti-freezing or anti-caking properties otherwise obtained by such formulations.

Specifically, we have found that one of the basic anticaking and anti-freezing additives disclosed in application Ser. No. 443,668 and consisting of Pluronic L35 (available from the Wyandotte Chemical C0., Wyandotte, Mich.), calcium chloride, and a water soluble complex iron cyanide may be combined with commercial grades of borax to produce an additive for bulk particulate sodium chloride which possesses anti-caking and anti-freezing characteristics and in which the anti-corrosion effect surpasses that of conventional sodium chloride brine corrosion inhibitors.

A preferred embodiment of this invention is as follows:

Lbs. Calcium chloride 4 Sodium ferrocyanide decahydrate .4 Pluronic L-35 .l Borax 5 and when these materials are thoroughly mixed with and added in the amount specified to one ton of bulk particulate sodium chloride, corrosion associated with the brine solutions formed from such treated sodium chloride will be less than brine solutions formed from sodium chloride treated with sodium hexametaphosphate in an amount more than twice as great as the above amount (sodium hexametaphosphate is conventionally used at a level of 20 pounds per ton of sodium chloride for anti-corrosion purposes). The amount of borax may be varied to constitute as little as two pounds per ton and is most effective within the limits of 2-5# per ton.

The proportion of the calcium chloride, water soluble complex iron cyanide and Pluronic L-35, as pointed out in copending application 443,668, may be varied. The calcium chloride must be present at least in the amount which would constitute three pounds of calcium chloride per ton of sodium chloride, taking into consideration the amount of calcium chloride which may be present naturally in the sodium chloride. The water soluble complex iron cyanide should be present in the range of about .l3.22 pound of ferrocyanide ion per ton of sodium chloride.

Pluronic L is a block type copolymer of ethylene and propylene oxides and may be made according to the disclosure of Pat. No. 2,674,619. In general, the material is prepared by adding propylene oxide to the two hydroxyl groups of a propylene glycol nucleus. To both ends of this resulting hydrophobic base are added hydrophilic polyoxyethylene groups to constitute 50% of the final molecule. The molecular weight of the copolymer is approximately 1900.

The term borax as used herein is meant to encompass sodium tetraborate decahydrate as well as sodium tetraborate pentahydrate. Although borax is well known as a rust inhibitor for use in conjunction with water as for example is a soft drink and brewery industry, and is also well known as a rust inhibitor in anti-freeze solutions such as synthetic methanol, ethylene glycol, ethanol, isopropanol, propylene glycol and diethylene glycol, we have found that its use in association with brine solutions yields highly non-uniform results and in many instances of particularized brine strengths actually enhances corrosion. However, the compositions according to the present invention which include borax not only lend a greater anti-corrosion effect than can be attributed to borax alone, but they also reduce the variation in corrosion effects and completely eliminate any enhancement of corrosion which can be attributed to borax in certain brine strengths. Moreover, although the anti-freeze additives according to the aforementioned co-pending applications exhibit, in themselves, some anti-corrosion effect, their effect is not nearly as great as the compositions according to the present invention and, as a matter of fact, as between the anti-freeze additives of the copending applications and the use of borax, the combining of these two ingredients in accord with the present invention attains an anti-corrosion effect which is substantially greater than the sum of the two when used individually. As compared with conventional anti-corrosion agents used with sodium chloride brines, the present invention achieves the important advantages of being non toxic and nonpolluting as well as being less expensive.

Lit

What is claimed is:

1. An additive for inhibiting caking and freezing tend encies of bulk particulate sodium chloride and for inhibiting corrosion which may occur incidental to the formation of brine solution therefrom, which consists of:

one part by weight of a block type polyol copolymer of ethylene and propylene oxides having a molecular weight of about 1900 and substantially equal amounts of the two oxides,

about 30-200 parts by weight of calcium chloride,

ferrocyanide ion in about 1.3-8.8 parts by weight obtained from sodium ferrocyanide decahydrate as a source therefor,

and about 2050 parts by weight of a borax compound.

2. The additive according to claim 1 wherein the calcium chloride is present in the amount of 40 parts by weight, the source of ferrocyanide ion is present in the amount of 4 parts by weight and the borax compound is sodium tetraborate decahydrate in the amount of parts by weight.

References Cited UNITED STATES PATENTS 3,231,501 1/1966 Reeso 252387 2,104,619 1/1938 Lehmann l- 2152-385X 2,988,509 6/1961 Schilberg 252 3,009,775 11/1961 Ladenburg et a1. 252383X 3,036,884 5/1962 Kaufmann 252-385X 3,090,756 5/1963 Kaufmann 252-70X 3,240,558 3/1966 Heiss et al. 252-384X 3,310,494 3/1967 Sproule et al. 252-70 1,724,551 8/1929 Bellis 252-71 1,724,552 8/1929 Bellis 252-7l 2,793,147 5/1957 Erdmann et al. 25271X 3,033,670 5/1962 Stanford et al 252387X 3,362,910 1/1968 Ordolt et al. 252-387X 3,378,493 4/1968 Jacoby et al. 25270 OTHER REFERENCES The Condensed Chemical Dictionary, Reinhold, 1961, 6th edition, p. 1036.

RICHARD D. LOVERING, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3, 512 Dated January 26 1971 Inventor s Charles H. Jacoby et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 59, "3 ,396 ,112" should read 3,396 ,113 Column 3, line 23, "is" should read in Signed and sealed this 29th day of June 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCI-IUYLER, Q Attesting Officer Commissioner of Paten1 

